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Digitized  by  the  Internet  Archive 

in  2012  with  funding  from 

University  of  Illinois  Urbana-Champaign 


http://archive.org/details/carbonratiospetr5574moul 


STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

A.  M.  SHELTON,  Director 

DIVISION  OF  THE 

STATE  GEOLOGICAL  SURVEY 

M.  M.   LEIGHTON.  Chief 
REPORT  OF  INVESTIGATIONS-NO.  4 

CARBON  RATIOS  AND  PETROLEUM 
IN  ILLINOIS 

BY 
GAIL  F.  MOULTON 


PRINTED  BY  AUTHORITY  OF  THE  STATE  OF  ILLINOIS 


URBANA,  ILLINOIS 
1925 


STATE  OF  ILLINOIS 
DEPARTMENT  OF  REGISTRATION  AND  EDUCATION 

DIVISION  OF  THE 

STATE  GEOLOGICAL  SURVEY 

M.  M.  LEIGHTON,  Chief 


Committee   of  the   Board   of  Natural  Resources 
and  Conservation 

A.  M.  Shelton,  Chairman 

Director   of   Registration    and    Education 

Kexdric  C.  Babcock 

Representing   the   President   of  the  Uni- 
versity of  Illinois 

Edson  S.  Bastin 
Geologist 


Schnepp  &  Barnes,  Printers 

Springfield,  III. 

1925 

43276—1000 


GAR  HON  RATIOS  AND  PETROLEUM 
IN  ILLINOIS 

By  Gail   F.   Moulton 


OUTLINE 

[•AG  E 

Introduction 5 

Use   of  data    5 

Sources  of  information 5 

Accuracy   of   carbon    ratios 6 

Structural   features   of   Illinois 10 

Relation  of  oil  fields  to  structural  features 11 

Fields  along  the  La  Salle  anticline 11 

Minor    western    fields 11 

Relation  of  coal  character  to  structural  features 11 

Carbon    ratios    11 

Moisture   content    14 

Isohume   determinations    from    carbonaceous    shales 14 

Conclusions   concerning   oil    possibilities 15 

Choice   of  limiting  ratios 15 

Areas  appearing  to  have  special  merits 17 

Value   of  carbon   ratios 18 

ILLUSTRATIONS 

FIGURE 

1.  Generalized   structure   map   of   Illinois 8 

2.  Illinois   oil  and  gas   fields 9 

3.  Isocarb  map  of  Illinois  for  No.  6  coal 12 

4.  Isohume  map  of  Illinois  coal 13 

5.  Horizons  with  oil  possibilities  according  to  carbon  ratios 16 

TABLES 

1.  Variations  of  carbon  ratios  between  the  various  coals  in  Illinois 7 

2.  Relation  of  carbon  ratios  to  sand  and  oil  character 15 

3.  Limiting  carbon  ratios  for  oil  producing  horizons  in  certain  localities..  17 


INTRODUCTION 

In  the  decade  since  White1  first  called  attention  to  the  interrelation  of 
the  effects  of  metamorphism  on  coal  and  petroleum,  the  relation  has  been 
further  investigated  in  several  of  the  important  oil  producing  states.  Thus 
far,  carbon  ratios  (the  ratio  of  Fixed  Carbon  to  the  sum  of  Fixed  Carbon 
plus  Volatile  Matter)  have  been  very  useful  in  pointing  out  areas  in  which 
the  processes  of  metamorphism  have  been  so  pronounced  that  the  chances 
of  rinding  commercial  accumulations  of  petroleum  are  slight.  The  possi- 
iblity  of  their  use  in  locating  areas  of  greater  deformation  favorable  to  oil 
occurrence  in  regions  of  slight  folding,  has  not  been  stressed,  but  also  de- 
serves consideration. 

Petroleum  investigations  in  Illinois  are  greatly  hampered  by  the  occur- 
rence of  the  thick  cover  of  glacial  drift  and  the  shallow  dissection  of  the 
surface.  Detailed  determinations  of  structural  conditions  have  depended 
largely  upon  the  interpretation  of  well  logs.  For  considerable  areas  in  the 
State,  such  information  is  scanty  and  not  very  reliable.  Consequently,  it 
seems  desirable  to  investigate  carbon  ratios  in  Illinois  coals  to  assist  in  de- 
lineating areas  in  which  general  deformation  has  occurred.  In  such  areas 
the  chances  of  finding  structures  suitable  for  the  accumulation  of  petroleum 
would  be  greater  than  in  relatively  undisturbed  areas,  and  special  attention 
would  be  deserved. 

In  addition  to  the  question  of  choice  of  areas  for  further  investigation, 
carbon  ratios  have  possibilities  in  helping  to  solve  several  related  problems 
such  as  :  (  1  )  consideration  of  possibilities  of  oil  production  in  the  faulted 
area  in  southern  Illinois;  (2)  the  deepest  horizon  which  should  be  tested 
in  favorable  structures  in  various  regions  of  the  State;  (3)  relation  between 
carbon  ratios  and  moisture  content  of  coals;  (I)  the  effects  of  depth  of 
burial  and  unconformities  on  carbon  ratios,  and  (5)  the  reason  for  the 
dominance  of  gas  production  in  western  Illinois  as  contrasted  with  that  of 
oil  in  eastern  Illinois. 

USE  OF  DATA 

Sources  of  Information 

For  a  number  of  years  Illinois  has  held  an  important  place  as  a  coal 
producer.  Consequently,  a  large  amount  of  information  is  available  con- 
cerning the  character  of  the  coal.     Most  of  the  analyses  have  been  compiled 

•Whit.,    David,   Some   relations   in   origin   between   coal   and    petroleum:    Wash.    Acad. 
Bci.  Jour.  Vol.  6,  pp.   189-212,   1915. 


6  CARBON    RATIOS    AND    PETROLEUM     IN     ILLINOIS 

and  published.2  Carbon  ratios  were  computed  from  the  original  analyses 
for  about  350  mines,  and  in  mosl  cases  the  re  nil  used  was  an  average  of 

three  or  more  analyses.  All  of  the  analyses  used  were  made  either  by  the 
U.  S.  Bureau  of  Mines  or  the  Fuel  Laboratory  of  the  University  of  Illi- 
nois. The  close  agreemenl  of  results  obtained  by  these  two  laboratories  is 
probably  not  excelled  by  any  other  two  in  the  country.  For  that  reason  the 
data  used  are  of  uniformly  high  quality. 

\('(  URACY   OP'  CaI  BON    1\  VTIOS 

The   uncertainty    i  ;    carbon    ratio    value   corresponding   to    permissible 

variations  in  the  results  of  analysis  was  calculated  in  order  to  de  ermine  the 
minimum  change  in  carbon  ratio  which  should  he  considered  significant. 
The  method  of  computing  this  minimum  is  as  follows: 

Let  A  he  the  volatile  matter,  B  the  fixed  carbon,  and  D  the  ash  plus 
moisture.  Then  A  +  B-f  ')  -  100  per  cent  and  B  /  (A  +  B  )  =  the 
carbon  ratio.  In  order  to  determine  the  variation  due  to  permissible  errors 
in  analysis,  the  use  of  simple  differen  ial  ca'culus  is  advisable.  The  equa- 
tions which  follow  show  the  steps  taken  in  deriving  the  formula. 

B  100—  (A  +D) 

= (Two      expressions      for      the     carbon      ratio) 

A  +  B  100  —  /) 

Differentiating: 

B  \  (100  —  D)    (  —  dA   —  <W)    +    (100  —  .1    —  D)    (ID 


„(-£-) 

V  (A    +  B)   / 

<  (-M 

\U   +  B)   J 


(100  —  D)- 
or 

B  \      (100  —  ID   dA   --  lOOdD   +  DdD   +   100  dl)  —  AdD  —  DdD 


(100  —  D)' 

(100   —  D)  (1A    +    Ad  I)               iIA  AdD 

Combining     like     terms     gives = + 


(100—")-  100—  D         (100  —  uy 

<1A  AdD 

or   the    uncertainty    of    carbon    ratio   = +    in    which    dA    is 

100  —  D  (100  —  DY- 

the  permissible  error  in  volatile  matter  and   dD  is  the  permissible  error   in  non- 
combustible  matter. 

For  Illinois  coals  the  standard  limits  of  error  give  the  values  dA= 
1.00  per  cent,  and  dD=0.8  per  cent.  By  using  these  values  and  taking  the 
value  for  I)  and  A  from  the  analyses  of  various  Illinois  coals,  the  uncertainty 
in  carbon  ratio  was  found  to  vary  from  1.18  to  1.38  according  to  the  local 
condition  of  the  coal. 

If  each  datum  point  on  the  map  (fig.  3)  had  only  one  analysis  as  its 
source  of  information,  variations  in  carbon  ratios  of  1.25  per  cent  would 
he  of  doubtful  significance.     The  values  used,  however,  were  the  result  of) 


!Hawley,  G.  W.,  Analyses  of  Illinois  coals:   111.  Jlin.   Investigations  Bull.   27A,   1928 
(Includes  analyses  previously   published  by   tin-  r.   S.   Bureau  of  Mines.) 


CARBON    RATIOS   AND    PETROLEUM     IX    ILLINOIS  . 

averaging  several  analyses.  This  process  reduced  the  probable  error  to  at 
least  one-half  the  computed  limit.  Accordingly,  variations  of  one  per  cent 
in  carbon  ratio  are  considered  significant,  and  fairly  uniform  changes  of 
smaller  value  are  worth  notice.  In  order  to  show  all  authentic  details  of 
carbon  ratio  variation,  isocarbs  were  drawn  at  intervals  of  two  per  cent. 

The  law  of  Hilt,  that  there  is  a  progressive  increase  of  fixed  carbon  in 
successively  older  coal  beds  in  passing  downward  in  a  stratigraphic  section, 
was  considered  in  Illinois.  David  White3  cites  several  exceptions.  If  the 
law  is  exact,  the  increase  in  carbon  ratio  from  one  coal  to  the  next  in  a  con- 
formable series  would  depend  on  the  stratigraphic  interval.  If  an  uncon- 
formity occurs  between  two  coals,  the  lower  should  show  an  abrupt  increase 
in  carbon  ratio. 

In  Illinois  several  coal  beds  are  important  enough  to  be  mined.  In  a 
few  localities  samples  from  two  or  more  coals  have  been  analysed.  These 
analyses  have  been  compared  to  check  the  law  of  Hilt  and  to  determine  the 
carbon  ratio  correction  for  coals  other  than  No.  (i.  Although  in  certain 
cases  modifications  of  results  were  probably  introduced  by  errors  in  coal 
correlation,  a  preliminary  suggestion  of  the  effects  on  carbon  ratios  was  ob- 
tained. These  are  shown  in  Table  1.  Illinois  coals  have  been  given  con- 
secutive numbers  beginning  with  No.   1   at  the  bottom. 

Table  1.     Variations  of  carbon  ratios  between  the  various  coals  in  Illinois 


County 

Cot 

1 

Carbon 
ratio 

Comments  on  variations 

Fulton 

No. 

5 

51.7 

No  significant  difference 

No. 

1 

51.8 

McLean 

No. 

5 

48.8 

No  significant  difference 

No. 

2 

49.6 

Gallatin 

No. 

6 

57.4 

Increase  of  1.3  marks  unconformity 

No. 

5 

58.7 

Vermilion 

No. 

7 

50.8 

Increase  of  2.3  marks  unconformity 

No. 

6 

53.1 

Jackson 

No. 

6 

57.4 

Increase  of  2.8  marks  unconformity 

No. 

2 

60.2 

As  a  result  of  a  consideration  of  the  available  data  in  Illinois,  it  appears 
that  the  effect  of  the  difference  in  depth  is  not  significant  if  the  series  is  con- 


White,   David,  The  origin  of  coal:   U.  S,    Bur.   Mines   Hull.   :;s;.   pp.    125-1! 


1913. 


CARBON    RATIOS   AND   PETROLEUM    FN    [LLINOIS 


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ILLINOIS  J  ogle 

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-I-trM  V 

'      ILL 


WILLIAMSON  |     SALINE 

L-Zone  of 
.       HXfoScN    faulting 
JOMNSONpyfEI-'^J 


Fig.  1.    Centralized   structure  map  of  Illinois.     Contours  on 
approximate  horizon  of  No.  2  coal. 


CARBON    RATIOS  AND   PETROLEUM    IN    ILLINOIS 


Fig.  2.    Illinois  oil  and  gas  fields. 


10  CARBON    RATIOS    AND    PETROLEUM    IN    ILLINOIS 

formable.  This  apparent  exception  to  the  law  of  Milt  may  arise  from  the 
small  thickness  of  beds  between  the  coals  sampled  (about  250  feet,  maxi- 
mum) or  may  be  clue  to  a  lack  of  critical  data.  In  case  the  coals  arc  sepa- 
rated by  an  unconformity,  however,  there  is  a  marked  increase  in  carbon 
ratio  of  the  lower  coal.  These  differences  seem  to  be  pronounced  enough 
to  be  of  value  in  coal  correlation. 

No.  (i  coal  was  chosen  as  the  standard,  for  it  is  one  of  the  most  exten- 
sive beds  in  the  Siate.  Because  the  No.  <i  coal  is  separated  from  both  the 
underlying  and  overlying  coals  by  an  unconformity,  a  correction  is  necessary 
in  the  carbon  ratios  of  the  other  coals  in  order  that  the  results  may  be  com- 
parable. The  following  corrections  were  applied  to  reduce  results  to  No.  6 
coal : 

Gallatin  County — Subtract  1.3  from  carbon  ratios  of  No.  5  coal. 

Vermilion  County — Add  2.3  to  carbon  ratios  of  No.  7  coal. 

Jackson  County — Subtract  2.8  from  No.  2  coal  carbon  ratio. 
These  ratio  corrections  were  also  applied  to  coals  in  the  vicinity  of  the  places 
For  which  they  were  determined. 

STRUCTURAL  FEATURES  OF  ILLINOIS 

In  order  to  appreciate  fully  the  significance  of  the  carbon  ratios  in  Illi- 
nois, it  is  first  desirable  to  have  a  general  idea  of  the  main  known  structural 
features  of  the  State  (  fig.  1  ),  so  that  the  relation  between  these  features  and 
the  configuration  of  the  isocarbs  will  he  apparent. 

The  La  Salle  anticline  is  one  of  the  most  prominent  structural  features 
of  Illinois.  It  may  be  traced  from  the  north  central  part  of  the  State  in  a 
direction  a  little  east  of  south  for  most  of  the  length  of  the  State  to  a  point 
where  it  crosses  Wabash  River  into  Indiana.  The  structural  contours  (fig. 
1  ),  show  that  the  dip  on  the  west  limb  of  the  fold  is  much  steeper  than  that 
on  the  east.  The  folding  along  this  axis  began  in  pre-Pennsylvanian  time, 
•but  was  continued  at  the  end  of  the  Pennsylvania!!  deposition,  so  that  the 
structure  in  the  lower  rocks  is  similar  to  that  of  the  coals,  hut  is  more  pro- 
nounced. 

The  Duquoin  anticline  is  another  prominent  fold.  It  extends  through 
the  south  central  portion  of  the  State  in  a  north-south  direction.  In  this 
case,  the  steeper  dip  is  on  the  east  side  of  the  fold.  As  figure  1  shows,  the 
west  side  is  rather  indefinite,  and  is  not  marked  by  west  dips. 

The  interior  basin  lies  between  the  steeply  dipping  east  limb  of  the 
Duquoin  anticline  on  the  west,  and  the  steeply  dipping  west  limb  of  the 
La  Salle  anticline  on  the  east,  and,  as  the  map  shows,  includes  a  large  part 
of  the  State.  In  most  portions  of  the  basin  the  coals  are  at  a  considerable 
depth.  This  is  due  to  both  the  structural  depression  and  greater  thickness 
of  the  Pennsylvanian  sediments.  The  greater  thickness  of  the  sediments  and 
the  greater  abundance  of  liner  clastic  materials  point  to  the  existence  of  this 
basin  during  the  early  Pennsylvanian  at  least. 


CARBON    RATIOS    AND    PETROLEUM     IN    ILLINOIS  1  1 

The  southern  zone  of  faulting  was  the  scene  of  more  vigorous  dynamic 
adjustments.  Complex  faulting  and  minor  igneous  activity  characterize  this 
region.  As  a  result  of  greater  relative  uplift,  the  Pennsylvanian  has  been 
largely  removed  from  this  area.  Only  along  the  north  edge  of  the  zone  of 
faulting  is  it  possible  to  determine  carbon  ratios.  Although  much  of  the 
faulting  may  be  post-Chester  and  pre-Pennsylvanian,  a  large  part  of  it  oc- 
curred after  the  close  of  the  Pennsylvanian.  Only  a  few  of  the  major  faults 
are  indicated  in  figure  1. 

RELATION  OF  OIL  FIELDS  TO  STRUCTURAL  FEATURES 
Fields  Along  the  La  Salle  Anticline 
As  might  be  expected  in  an  area  of  moderate  disturbance,  the  principal 
oil  fields  are  located  along  one  of  the  principal  lines  of  folding.  More  than 
ninety  per  cent  of  the  present  oil  production  of  the  State  comes  from  these 
fields  on  the  La  Salle  anticline.  For  various  reasons,  the  producing  area 
has  been  nearly  continuous  along  much  of  the  fold.  This  relation  is  strik- 
ingly brought  out  by  a  comparison  of  figures  1  and  '!,  which  show  the  loca- 
tion of  the  La  Salle  anticline  and  the  producing  area  respectively.  The  pro- 
ducing horizons  include  the  Trenton,  the  Kinderhook  and  the  Mississippian 
lime  of  the  lower  Mississippian,  the  Chester,  and  the  Pennsylvanian. 

Minor  Western  Fields 
Three  of  the  minor  pools  in   Illinois  are  located  on  and  near  a  broad 
northern  extension  of  the  Duquoin  anticline.     The  other  pools  in  the  west- 
ern part  of  the  State  are  located  on   folds  which  have  no  established  con- 
nection with  the  major  structural  features  of  the  State. 

RELATION  OF  COAL  CHARACTER  TO  STRUCTURAL 

FEATURES 

Carbon  Ratios 

A  comparison  of  the  structural  contours  in  figure  1  and  the  isocarbs 
in  figure  3  shows  that  the  zones  disturbed  by  folding  are  closely  followed 
by  increases  in  the  carbon  ratios  in  the  coal.  The  folding  of  the  La  Salle 
anticline  and  the  Duquoin  anticline  in  particular  have  caused  zones  of  high 
carbon  ratios  which  project  for  many  miles  into  areas  of  lower  carbon  ratios. 

The  isocarb  map  also  shows  clearly  that  the  disturbances  accompanied 
by  faulting  in  the  southern  part  of  the  State  caused  a  greater  regional  meta- 
morphism  than  is  general  in  the  central  and  north  parts  of  the  State. 

One  of  the  most  interesting  features  brought  out  by  the  isocarb  ma])  is 
the  tongue  of  high  carbon  ratios  which  extends  northwest  from  central 
Tazewell  County  to  Rock  Island  County.  The  existence  of  this  area  of 
higher  ratios  had  not  been  suspected  because  there  is  no  structural  feature 
of  major  importance  known  there.     It  would  appear  that  the  carbon  ratios 


12 


CARBON    RATIOS    AND    PETROLEUM     IN    ILLINOIS 


FlG.  3.     Isocarb  map  of  Illinois  for  No.   6  coal 


CARBON    RATIOS   AND    PETROLEUM    IN    ILLINOIS 


13 


Fig.  4.     Isohume  map  of  Illinois  coal. 


II  CARBON    RATIOS   AND    PETROLEUM     IX    ILLINOIS 

in  this  instance  will  be  useful  in  pointing  ou1  a  locality  deserving  inure  thor- 
ough investigation. 

Moisture  Content 

An  unpublished  map  drawn  by  (i.  II.  Cady  suggested  the  possibility  of 
using  the  moisture  content  of  coals  as  a  means  for  interpreting  the  effective- 
ness ol  metamorphism.  A  new  ma])  has  been  prepared,  making  use  of  more 
recent  available  data.  The  mapping  of  the  moisture  content  of  Illinois  coals 
did  not  give  as  satisfactory  results  in  all  parts  of  the  State  as  the  carbon 
ratios  did,  duv  probably  in  part  to  the  lack  of  consistent  handling  and  treat- 
ment of  the  samples  before  analysis.  In  Franklin  and  Williamson  coun- 
ties the  results  were  more  satisfactory.  As  a  large  number  of  analyses 
would  tend  to  help  average  out  errors,  such  regions  should  show  the  besl 
results. 

In  analysis,  the  permissible  error  in  moisture  determination  is  ().:i  per 
cent  for  coals  of  the  type  found  in  Illinois.  An  examination  of  the  results 
of  moisture  determinations  suggests  that  ordinarily  variations  of  L.5  per  cent 
may  he  considered  significant.  Accordingly,  the  lines  connecting  points  of 
equal  moisture  content  were  drawn  at  intervals  of  two  per  cent. 

For  convenience,  it  is  proposed  to  call  the  lines  connecting  points  of 
equal  moisture  "isohumes".  The  isohumes  shown  in  figure  4  are  very 
closely  parallel  to  the  isocarbs  (fig.  3),  It  should  be  noted  that  the  value 
of  the  isohumes  decreases  as  regions  of  greater  metamorphism  are  ap- 
proached, and  that  this  is  in  direct  contrast  to  the  changes  in  carbon  ratios. 
Also,  the  value  of  the  isohumes  is  subject  to  more  considerable  variations 
as  the  critical  carbon  ratios  are  approached.  This  is  well  shown  in  south- 
ern  Illinois,  where  die  isohumes  are  closer  together  than  the  isocarbs. 

I  SOUL' MI-".  DETERMINATIONS  FROM  CARBONACEOUS 

SHALES 

Several  points  should  he  considered  in  connection  with  the  possibility 
of  using  the  moisture  content  of  coals  and  other  carbonaceous  rocks,  as  an 
indicator  of  the  effectiveness  of  metamorphism.  First,  the  carbon  ratios  of 
impure  coals  and  carbonaceous  shales  are  subject  to  great  variation,  due  to 
permissible  errors  in  analysis.  As  an  example,  may  he  cited  a  coal  with  a 
carbon  ratio  of  50  per  cent,  and  with  noncomhustihle  material  making  up 
90  per  cent  of  the  whole.  From  the  formula  previously  derived,  the  pos- 
sible  variation  in  carbon  ratio  is  found  to  he  13  per  cent.  This  fact  may  be 
the  explanation  of  the  failure  of  attempts  to  use  carbon  ratios  from  rich 
organic  shales. 

The  moisture  determination  would  not  he  affected  in  a  similar  manner, 
and  should  still  he  dependable  within  a  limit  of  I.-")  per  cent.  These  consider- 
ations suggest  that  standard  methods  for  the  sampling  of  fine  shales  and  the 
determination  of  moisture  content  should  he  established,  in  order  to  test 


CARBON    RATIOS    AND    PETROLEUM     IN    ILLINOIS 


15 


this  possible  means  of  measuring  the  effectiveness  of  metamorphism  in  re- 
gions which  have  no  coal.  In  view  of  the  fact  that  changes  in  metamor- 
phism near  the  critical  limit  for  petroleum  accumulation  have  a  marked 
effect  on  the  moisture  content,  this  method  of  attacking  the  problem  seems  to 
have  great  possibilities. 

CONCLUSIONS   CONCERNING   OIL   POSSIBILITIES 
Choice  of  Limiting  Ratios 

The  effect  of  metamorphism  at  depths  below  the  coals  is  a  variable 
factor  which  may  be  a  serious  obstacle  to  the  unrestricted  use  of  carbon 
ratios  in  outlining  the  possible  oil  areas  in  Illinois.  The  numerous  uncon- 
formities to  be  found  in  the  stratigraphic  section  require  some  rough  evalu- 
ation so  that  conclusions  can  be  reached  regarding  depths  to  which  drilling 
is  advisable  for  any  given  carbon  ratio.  Probably  the  simplest  and  most 
reliable  method  for  making  such  determinations  is  to  examine  conditions  in 
the  producing  fields  of  the  State,  and,  using  these  conditions  as  a  standard, 
to  detect  the  presence  of  local  variations  which  demand  an  adjustment  in 
the  carbon  ratio  limit  for  possible  oil  production.  From  such  information, 
it  is  proposed  to  estimate  the  effects  of  depth  and  unconformities  in  terms  of 
oil  possibilities. 

According  to  available  information,  most  of  the  Illinois  oil  production 
comes  from  areas  with  carbon  ratios  lying-  between  54  and  57  for  the  No.  6 
coal.  Table  2  shows  the  highest  carbon  ratios  known  near  producing  areas 
for  each  of  the  oil  sands. 

Table  2.     Relation  of  carbon  ratios  to  sand  and  oil  character 


Age 

County 

Depth 

Character 

Carbon 
ratio 

Gravity 
of  oil 

Chester 

Jackson 

850 

Porous  sand 

56 

(mainly 

gas) 

Degrees 
Bait  me 

Chester 

Wabash 

1400 

Porous  sand 

57 
(probably) 

35 

Mississippian 

Clark 

700 

Soft 

55 

32 

lime 

Mississippian 

Lawrence 

1700 

Open  lime- 
stone 

56 

lime 

Lowest   Mississippian 

Clark 

1400 

Fine  sandy 

55 

38.7 

(Kinderhook) 

siltstone 

Silurian 

McDonough 

430 

Open   sandy 
lime 

52 

Trenton 

Clark 

2300 

Hard,  tight 

55 

37 

Trenton 

Monroe 

500 

Coarsely 
crystal- 
line 

53 

30.1 

in 


CARBON    RATIOS   AND    PETROLEUM    IN    ILLINOIS 


Fig.  5.     Horizons  with  oil  possibilities  according  to  carbon  ratios. 


CARBON    RATIOS   AND    PETROLEUM    IX    ILLINOIS 


1 


Certain  relations  are  suggested  by  the  tabulated  information.  First,  it 
seems  probable  that  the  Trenton  of  eastern  Illinois  has  not  been  a  good  oil 
producer,  because  the  metamorphism  active  there  made  a  substantial  reduc- 
tion in  the  natural  porosity  of  the  rock.  In  Monroe  County,  metamorphic 
effects  were  not  as  great,  so  the  Trenton  is  more  open  and  productive.  The 
carbon  ratios  indicate  this  relation.  Second,  the  difference  in  the  character 
of  the  production  found  in  the  Chester  in  Wabash  and  in  Jackson  counties 
may  be  explained  as  due  to  a  greater  amount  of  pre-Pennsylvanian  move- 
ment in  the  latter  place.  Certainly  in  southwestern  Illinois,  there  was  pre- 
Pennsylvanian  folding,  and  recent  work  indicates  that  it  was  accompanied 
by  faulting.4  Nothing  very  definite  is  known  about  the  transition  in  south- 
eastern Illinois,  but  the  occurrence  of  heavier  oil  is  suggestive  of  milder  con- 
ditions. If  this  variation  leads  to  the  conclusion  that  such  a  difference  in 
effectiveness  of  the  pre-Pennsylvanian  movements  did  exist,  then  it  is  neces- 
sary to  take  a  lower  carbon  ratio  for  the  limit  of  possible  Chester  produc- 
tion in  the  southwestern  part  of  the  State  than  in  the  southeastern.  Ac- 
cordingly, figure  5  showing  zones  with  various  possible  producing  horizons 
does  not  have  the  boundaries  of  those  zones  strictly  parallel  to  the  isocarbs. 

In  determining  the  lowest  horizon  with  possibilities  of  oil  production, 
the  following  carbon  ratios  were  chosen  as  limits: 

Table  3.     Limiting  carton   ratios   for  oil  producing  horizons   in   certain    localities 


Horizon 

Limiting  value 

Locality 

Pennsylvanian 

62 

Southern  Illinois 

Chester 

58 

Southwestern  Illinois 

Chester 

59 

Southeastern  Illinois 

Lower  Mississippian 

56 

Southwestern  Illinois 

Lower  Mississippian 

57 

Southeastern  Illinois 

Silurian-Devonian 

55 

Southwestern  Illinois 

Smirian-Devonian 

56 

Other  parts 

Trenton 

54 

Southwestern  Illinois 

Trenton 

55 

Other  parts 

Areas  Appearing  to  Have  Special  Merits 

In  searches  for  new  oil  pools  in  Illinois,  it  will  probably  be  advisable 
generally  to  limit  consideration  to  areas  having  oil  possibilities  at  least  in  the 
Chester,  and  preferably  in  the  lower  rocks  as  well.     Further,  a  concentration 


4  Ekblaw,    G.    E..    Post-Chester,    pre-Fennsylvanian    faulting    in    the    Alto    Pass    area  : 
State   Acad.   Sci.,   Springfield   Meeting,    1025. 


L8  CARBON    RATIOS   AND    L'ETKOLEUM     IX    ILLINOIS 

nf  attention  on  certain  zones  of  locally  higher  carbon  ratios  is  desirable  and 
justified.      Such  areas  are  the  central  pari  of  the  La  Salle  anticline,  the  north- 
ern part  of  the  Duquoin  anticline,  and  the  area  of  high  carbon  ratio  exte  id 
ing  from  Tazewell  County  to  Rock  Island  County. 

Value  of  Carbon  Ratios 

Carbon  ratios  of  Illinois  coals  change  in  such  a  manner  that  the  isocarbs 
parallel  the  structural  contours.  On  the  basis  of  the  carbon  ratios,  it  is 
possible  lo  eliminate  deep  testing  in  certain  areas,  and  to  eliminate  other 
areas  entirely  as  probable  oil  producers,  even  if  favorable  structural  features 
should  be  found.  An  equally  useful  result  is  that  some  of  the  areas  of 
greatest  promise  are  outlined. 


:CHER'S" 

IBRARY  BINDERS 
507  3.  Goodwin 
UrbanB,IlL 


